As reported on The Verge.
By Jacob Kastrenakes
That means photos flagged as potentially being modified span a wide range of possibilities. It isn’t only complex edits that Izitru might flag, but also photos that have been saved for a second time, even without any actual edits to them. Izitru also refrains from speaking definitively about modifications: images will, at most, be flagged as potential modifications until they’re reviewed by an expert, which Izitru says may happen if an image receives enough community attention. Even so, it’s still a simple tool that should be able to let you know when something in a photo may have been tampered with.
Izitru detects that this image of Jeff Goldblum’s body with another person’s face edited onto it may have been modified. Below the image it explains: “Our forensic tests suggest this file has been re-saved since initial capture. Because this file is not a camera original, it is possible that it was modified.”